1. Field of the Invention
The invention relates to an injector for injecting fuel into combustion chambers.
2. Description Of The Prior Art
European Patent Disclosure EP 1 612 403 A1 describes a common rail injector with a control valve, in pressure equilibrium in the axial direction, for blocking and opening a fuel outflow course from a control chamber. By means of the control valve, the fuel pressure inside the control chamber can be varied. The control chamber is supplied via a pressure conduit with fuel from a pressure chamber communicating hydraulically with a high-pressure fuel reservoir. Varying the fuel pressure inside the control chamber adjusts a nozzle needle between an opening position and a closing position; in its opening position, the nozzle needle enables the flow of fuel into the combustion chamber of an internal combustion engine. The control valve has a valve sleeve, which is adjustable in the axial direction by means of an electromagnetic drive and which cooperates with a stationary, conical valve seat face in a sealing fashion. In long-term use of the known injector, wear can be observed in the region of the valve seat. Because of the seat wear, a circular-annular surface develops on both the valve seat and the valve sleeve, and as a consequence the control valve is no longer in pressure equilibrium, and the opening characteristic of the control valve is subject to major changes over the service life of the injector. The opening behavior of the control valve is highly pressure-dependent over the course of time, which leads to marked changes in the injection quantities.